A Chandra view of the clumpy reflector at the heart of the Circinus galaxy

We present a spectral and imaging analysis of the X-ray reflecting structure at the heart of the Circinus galaxy, investigating the innermost regions surrounding the central black hole. By studying an archival 200 ks Chandra ACIS-S observation, we are able to image the extended clumpy structure responsible for both cold reflection of the primary radiation and neutral iron Ka line emission. We measure an excess of the equivalent width of the iron Ka line which follows an axisymmetric geometry around the nucleus on a hundred pc scale. Spectra extracted from different regions confirm a scenario in which the dominant mechanism is the reflection of the nuclear radiation from Compton-thick gas. Significant differences in the equivalent width of the iron Ka emission line (up to a factor of 2) are found. It is argued that these differences are due to different scattering angles with respect to the line of sight rather than to different iron abundances.Comment: 6 pages, 4 figures, accepted for publication on MNRA

Subsampling needlet coefficients on the sphere

In a recent paper, we analyzed the properties of a new kind of spherical wavelets (called needlets) for statistical inference procedures on spherical random fields; the investigation was mainly motivated by applications to cosmological data. In the present work, we exploit the asymptotic uncorrelation of random needlet coefficients at fixed angular distances to construct subsampling statistics evaluated on Voronoi cells on the sphere. We illustrate how such statistics can be used for isotropy tests and for bootstrap estimation of nuisance parameters, even when a single realization of the spherical random field is observed. The asymptotic theory is developed in detail in the high resolution sense.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ164 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Asymptotics for spherical needlets

We investigate invariant random fields on the sphere using a new type of spherical wavelets, called needlets. These are compactly supported in frequency and enjoy excellent localization properties in real space, with quasi-exponentially decaying tails. We show that, for random fields on the sphere, the needlet coefficients are asymptotically uncorrelated for any fixed angular distance. This property is used to derive CLT and functional CLT convergence results for polynomial functionals of the needlet coefficients: here the asymptotic theory is considered in the high-frequency sense. Our proposals emerge from strong empirical motivations, especially in connection with the analysis of cosmological data sets.Comment: Published in at http://dx.doi.org/10.1214/08-AOS601 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

The defect variance of random spherical harmonics

The defect of a function $f:M\rightarrow \mathbb{R}$ is defined as the difference between the measure of the positive and negative regions. In this paper, we begin the analysis of the distribution of defect of random Gaussian spherical harmonics. By an easy argument, the defect is non-trivial only for even degree and the expected value always vanishes. Our principal result is obtaining the asymptotic shape of the defect variance, in the high frequency limit. As other geometric functionals of random eigenfunctions, the defect may be used as a tool to probe the statistical properties of spherical random fields, a topic of great interest for modern Cosmological data analysis.Comment: 19 page

X-ray observations of the Compton-thick Seyfert 2 galaxy, NGC 5643

We present results from a ~55 ks long XMM-Newton observation of the obscured AGN, NGC 5643, performed in July 2009. A previous, shorter (about 10 ks) XMM-Newton observation in February 2003 had left two major issues open, the nature of the hard X-ray emission (Compton-thin vs Compton-thick) and of the soft X-ray excess (photoionized vs collisionally ionized matter). The new observation shows that the source is Compton-thick and that the dominant contribution to the soft X-ray emission is by photoionized matter (even if it is still unclear whether collisionally ionized matter may contribute as well). We also studied three bright X-ray sources that are in the field of NGC 5643. The ULX NGC 5643 X-1 was confirmed to be very luminous, even if more than a factor 2 fainter than in 2003. We then provided the first high quality spectrum of the cluster of galaxies Abell 3602. The last source, CXOJ143244.5-442020, is likely an unobscured AGN, possibly belonging to Abell 3602.Comment: 6 pages. Accepted for publication in A&

High frequency asymptotics for wavelet-based tests for Gaussianity and isotropy on the torus

We prove a multivariate CLT for skewness and kurtosis of the wavelets coefficients of a stationary field on the torus. The results are in the framework of the fixed-domain asymptotics, i.e. we refer to observations of a single field which is sampled at higher and higher frequencies. We consider also studentized statistics for the case of an unknown correlation structure. The results are motivated by the analysis of high-frequency financial data or cosmological data sets, with a particular interest towards testing for Gaussianity and isotropy. (c) 2007 Elsevier Inc. All rights reserved

The changing X-ray time lag in MCG-6-30-15

MCG-6-30-15 is one of the most observed Narrow Line Seyfert 1 galaxies in the X-ray band. In this paper we examine the X-ray time lags in this source using a total of 600 ks in observations (440 ks exposure) taken with the XMM-Newton telescope (300 ks in 2001 and 300 ks in 2013). Both the old and new observations show the usual hard lag that increases with energy, however, the hard lag turns over to a soft lag at frequencies below ~1e-4 Hz. The highest frequencies (~1e-3 Hz) in this source show a clear soft lag, as previously presented for the first 300 ks observation, but no clear iron K lag is detected in either the old or new observation. The soft lag is more significant in the old observation than the new. The observations are consistent with a reverberation interpretation, where the soft, reflected emission is delayed with respect to the hard powerlaw component. These spectral timing results suggest that two distinct variability mechanisms are important in this source: intrinsic coronal variations (which lead to correlated variability in the reprocessed emission), and geometrical changes in the corona. Variability due to geometrical changes does not result in correlated variability in the reflection, and therefore inhibits the clear detection of an iron K lag.Comment: Resubmitted to MNRAS after minor corrections. 11 pages, 10 figure

The Social Exclusion Bench Tool (SEBT): A visual way of assessing interpersonal social exclusion

People usually prefer to appear with an inclusive and positive attitude to others’ eyes. For this reason, the self-report scales assessing social exclusion intentions are often biased by social desirability. In this work, we present an innovative graphical tool, named Social Exclusion Bench Tool (SEBT), for assessing social exclusion not influenced by social desirability. The tool is based on the consistency between social distance and physical distance evaluation. The results showed that in two samples of adults from Italy (N = 252) and the UK (N = 254), the SEBT positively correlated with self-report measures of social exclusion, but not with the social desirability measure. The tool has been preliminarily evaluated in the context of social exclusion toward migrant people, but it appears a promising instrument for assessing social exclusion intentions toward different social groups. • The self-report scales assessing social exclusion intentions are often biased by social desirability. • The Social Exclusion Bench Tool (SEBT) is an innovative visual instrument for assessing social exclusion that seems not to be influenced by social desirability. • The tool appears a promising instrument for assessing social exclusion intentions toward different social groups

On Nonlinear Functionals of Random Spherical Eigenfunctions

We prove Central Limit Theorems and Stein-like bounds for the asymptotic behaviour of nonlinear functionals of spherical Gaussian eigenfunctions. Our investigation combine asymptotic analysis of higher order moments for Legendre polynomials and, in addition, recent results on Malliavin calculus and Total Variation bounds for Gaussian subordinated fields. We discuss application to geometric functionals like the Defect and invariant statistics, e.g. polyspectra of isotropic spherical random fields. Both of these have relevance for applications, especially in an astrophysical environment.Comment: 24 page

NGC 1068: No change in the mid-IR torus structure despite X-ray variability

Context. Recent NuSTAR observations revealed a somewhat unexpected increase in the X-ray flux of the nucleus of NGC 1068. We expect the infrared emission of the dusty torus to react on the intrinsic changes of the accretion disk. Aims. We aim to investigate the origin of the X-ray variation by investigating the response of the mid-infrared environment. Methods. We obtained single-aperture and interferometric mid-infrared measurements and directly compared the measurements observed before and immediately after the X-ray variations. The average correlated and single-aperture fluxes as well as the differential phases were directly compared to detect a possible change in the structure of the nuclear emission on scales of $\sim$ 2 pc. Results. The flux densities and differential phases of the observations before and during the X-ray variation show no significant change over a period of ten years. Possible minor variations in the infrared emission are $\lesssim$ 8 %. Conclusions. Our results suggest that the mid-infrared environment of NGC 1068 has remained unchanged for a decade. The recent transient change in the X-rays did not cause a significant variation in the infrared emission. This independent study supports previous conclusions that stated that the X-ray variation detected by NuSTAR observations is due to X-ray emission piercing through a patchy section of the dusty region.Comment: 6 pages, 5 figures, 3 tables. Accepted for publication on A&